A more compelling reason to eliminate D:
If two that-clauses have the same referent, the second that may be omitted only if it serves the SAME GRAMMATICAL FUNCTION as the first that.

D: the dioxins that are currently uncontrolled and [that] North Americans are exposed to comes from the incineration of wastes.
Here, the that in brackets is omitted, but its presence is implied.
Both the first that and the omitted that have the same referent: dioxins.

The first that serves as a SUBJECT -- the subject of the verb are controlled -- conveying that DIOXINS ARE CONTROLLED.
The omitted that serves as an OBJECT -- the object of the preposition to -- conveying that North Americans are exposed TO DIOXINS.
Since the second that serves as an OBJECT, while the first that serves as a SUBJECT, the second that may NOT be omitted.
Eliminate D.

in option D, the usage of AND implies that two different things are happening. Here the Dioxins should be modified and correct usage should mention that dioxins to which people are exposed, come from....

GMATGuruNY wrote:A more compelling reason to eliminate D:
If two that-clauses have the same referent, the second that may be omitted only if it serves the SAME GRAMMATICAL FUNCTION as the first that.

D: the dioxins that are currently uncontrolled and [that] North Americans are exposed to comes from the incineration of wastes.
Here, the that in brackets is omitted, but its presence is implied.
Both the first that and the omitted that have the same referent: dioxins.

The first that serves as a SUBJECT -- the subject of the verb are controlled -- conveying that DIOXINS ARE CONTROLLED.
The omitted that serves as an OBJECT -- the object of the preposition to -- conveying that North Americans are exposed TO DIOXINS.
Since the second that serves as an OBJECT, while the first that serves as a SUBJECT, the second that may NOT be omitted.
Eliminate D.

Hi Mitch ,

Thanks for the wonderful explanation, one question.

If the second THAT CLAUSE may not be omitted in the sentence then can we choose option D as OA?

Please advise.

j_shreyans wrote:
Hi Mitch ,

Thanks for the wonderful explanation, one question.

If the second THAT CLAUSE may not be omitted in the sentence then can we choose option D as OA?

Even if D included the second that, its construction would be faulty.
The reason:
When that introduces a relative clause, it should not serve as the object of a preposition.

Incorrect: the table THAT John placed the vase ON
Here, that incorrectly serves as the object of the preposition on.
Conveyed meaning:
John placed the book ON THAT.
This construction is not valid:
When that introduces a relative clause, it should not serve as the object of a preposition.
To convey the intended meaning, a which-modifier is preferred.
Correct: the table ON WHICH John placed the vase

D, with the second that included:
the dioxins...THAT North Americans are exposed TO.
Here, that is serving as the object of the preposition to.
Conveyed meaning:
North Americans are exposed TO THAT.
This construction is not valid:
When that introduces a relative clause, it should not serve as the object of a preposition.
To convey the intended meaning, a which-modifier is preferred.
Correct: the dioxins TO WHICH North Americans are exposed

Hi Mitch ,

Thanks for the great explanation.

Just to be more clear, can you please give one example where two THAT CLAUSES occurs.

Thanks in advance.

j_shreyans wrote:Hi Mitch ,

Thanks for the great explanation.

Just to be more clear, can you please give one example where two THAT CLAUSES occurs.

Thanks in advance.

An OA in GMATPrep:
Neutrinos are harmless elementary particles THAT are produced in nuclear reactions and THAT interact very weakly with matter.